Implant delivery capsule

ABSTRACT

A delivery system for delivering a stent-mounted heart valve, or other implant, through an introducer sheath. The delivery system includes an elongate catheter supporting a capsule. The capsule contains the stent-mounted heart valve in the crimped condition. The capsule includes a protrusion extending from its outer surface for urging the sheath away from the outer surface capsule as it moves therethrough, thereby reducing an average peak push force resulting from advancement of the capsule through the sheath.

RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/331,564, filed Oct. 21, 2016, entitled “Implant-Delivery Capsule,”which claims the benefit of U.S. Provisional Application No. 62/246,510,filed Oct. 26, 2015, entitled “Implant Delivery Capsule,” the contentsdisclosure of which are hereby incorporated by reference in theirentirety.

FIELD

The present application concerns embodiments of a capsule and/ornosecone for use with an implant delivery catheter, and, in particular,a capsule and/or nosecone for reducing push forces associated withdelivery of a prosthetic heart valve through a delivery sheath.

BACKGROUND

Endovascular delivery catheter assemblies are used to implant prostheticdevices, such as a prosthetic valve, at locations inside the body thatare not readily accessible by surgery or where access without invasivesurgery is desirable. For example, aortic, mitral, tricuspid, and/orpulmonary prosthetic valves can be delivered to a treatment site usingminimally invasive surgical techniques.

An introducer sheath can be used to safely introduce a deliveryapparatus into a patient's vasculature (e.g., the femoral artery). Anintroducer sheath generally has an elongated sleeve that is insertedinto the vasculature and a housing that contains one or more sealingvalves that allow a delivery apparatus to be placed in fluidcommunication with the vasculature with minimal blood loss. Aconventional introducer sheath typically requires a tubular loader to beinserted through the seals in the housing to provide an unobstructedpath through the housing for a valve to be mounted.

Conventional methods of accessing a vessel, such as a femoral artery,prior to introducing the delivery system include dilating the vesselusing multiple dilators or sheaths that progressively increase indiameter. This repeated insertion and vessel dilation can increase theamount of time the procedure takes, as well as the risk of damage to thevessel.

One solution has been the development of radially expanding introducersheaths. For example, U.S. Pat. No. 8,790,387, which is entitledEXPANDABLE SHEATH FOR INTRODUCING AN ENDOVASCULAR DELIVERY DEVICE INTO ABODY and is incorporated herein by reference, discloses a sheath with asplit outer polymeric tubular layer and an inner polymeric layer, forexample in FIGS. 27A and 28. A portion of the inner polymeric layerextends through a gap created by the cut and can be compressed betweenthe portions of the outer polymeric tubular layer. Upon expansion of thesheath, portions of the outer polymeric tubular layer have separatedfrom one another, and the inner polymeric layer is expanded from afolded configuration into a substantially cylindrical tube.Advantageously, the sheath disclosed in the '387 patent can temporarilyexpand for passage of implantable devices and then return to its foldedconfiguration and associated starting diameter.

Expandable introducer sheaths, however, have some challenges. One ofthese challenges is that expandable sheaths can increase the amount offorce needed to advance the delivery apparatus—such as a deliverycatheter having mounted on its end a stent-mounted prosthetic heartvalve—to the deployment site. Push forces also need to be mediated inconventional introducer sheaths.

As a result, there is a need to address the push forces required fordelivery of implants through introducer sheaths.

SUMMARY

Disclosed herein is a delivery system for delivering a stent-mountedheart valve through an introducer sheath. The delivery system includesan elongate catheter supporting a capsule. The capsule contains thestent-mounted heart valve in the crimped condition. The delivery systemalso includes a nosecone with a tapered distal end and a proximal end.Surprisingly, the proximal end of the nosecone, despite having a largerprofile than the capsule, reduces an average peak push force foradvancing the delivery system through an introducer sheath.

In one embodiment, a delivery system for delivering a stent mountedheart valve through a sheath and into a patient vessel is provided. Thedelivery system includes an elongate catheter, a capsule and a nosecone.The elongate catheter has proximal and distal ends. The stent mountedheart valve is crimped at the distal end of the elongate catheter. Thecapsule extends around and encloses the crimped stent mounted heartvalve. The capsule has a distal end with a capsule diameter. Thenosecone includes a tapered distal end and a proximal end. The proximalend is engaged to the distal end of the capsule. Advantageously, thetapered distal end has a smooth continuous shape configured toprogressively urge the sheath outward. Also, the proximal end has anosecone maximum diameter greater than the capsule diameter so as toreduce an average peak push force resulting from advancement of thecapsule through the sheath.

The delivery system can also include an inner catheter extending throughthe elongate catheter, capsule and stent mounted heart valve. The innercatheter, sometimes called a nosecone catheter, supports the nosecone onits distal end. Distal advancement of the inner catheter relative to theelongate catheter advances the stent mounted heart valve out of thecapsule.

In another embodiment, the nosecone diameter is at least 1.002 times thecapsule diameter. And, the upper tolerance limit of the peak push forceis less than 40 Newtons and can even be less than 33 Newtons. Thedelivery system works particularly well when the sheath is an expandablesheath having a starting inner diameter less than the capsule diameter.

In another embodiment, the delivery system can include the expandabledelivery sheath. The expandable delivery sheath includes a central lumensized and configured to receive the elongate catheter, capsule andnosecone. The central lumen defines a starting inner diameter less thanthe capsule diameter. The sheath can be a 16 FR sheath and the elongatecatheter can have a diameter from 23 mm to 29 mm.

The nosecone can, in one embodiment, include a progressive expansionportion, a rounded portion and an inflection point. The inflection pointcorresponds with or defines the nosecone maximum diameter. Also, theprogressive expansion portion can be on the distal end of the nosecone,the rounded portion adjacent and proximal the progressive expansionportion and the inflection point is proximal the rounded portion. Evenmore proximal, the nosecone can include a proximal end proximal theinflection point and with a shrinking diameter relative to the maximumnosecone diameter.

Another embodiment includes, in addition to or as an alternative of theenlarged nosecone, one or more protrusions positioned on a distal regionof the capsule and extending circumferentially around the capsule. Theprotrusion has a smooth continuous shape and is configured to urge thesheath away from the remainder of the capsule. The protrusion, forexample, can be a ring extending circumferentially around an exteriorsurface of the capsule. Advantageously, the protrusion(s) reduce anaverage peak push force resulting from advancement of the capsulethrough the sheath. The protrusions can also have a greatest diameterthat is at least 1.002 times the capsule diameter. Also, the uppertolerance limit of the peak push forces can be less than 40 Newtons, oreven less than 33 Newtons.

Another embodiment includes, in addition to or as an alternative of theenlarged nosecone, a plurality of longitudinally extending ridges. Theridges protrude from the surface of the capsule. The ridges areconfigured to space the capsule surface from the sheath as it movesthrough the sheath. This reduces an average peak push force resultingfrom advancement of the capsule through the sheath. The ridges can alsohave a greatest diameter that is at least 1.002 times the capsulediameter. Also, the upper tolerance limit of the peak push forces can beless than 40 Newtons, or even 33 Newtons. In another aspect, the ridgesinclude at least 6 ridges. The ridges can have a rectangularcross-sectional shape and extend around the circumference of the capsuleso as to define alternating troughs and ridges.

Another embodiment includes a method of assembling a stent mounted heartvalve onto a delivery system. The method includes providing a stentmounted heart valve supported by the delivery system. A nosecone is alsoprovided. The nosecone has a tapered distal end and a proximal end. Thetapered distal end has a smooth, continuous shape. The proximal enddefines a nosecone maximum diameter. The method also includes advancinga distal open end of a capsule of the delivery system over the stentmounted heart valve until the distal open end of the capsule abuts thenosecone and the capsule surrounds the stent mounted heart valve. Thecapsule defines a diameter smaller than a maximum diameter of thenosecone.

The method can also include advancing the nosecone through an expandabledelivery sheath by progressively urging the sheath outward with thesmooth continuous shape of the nosecone to an inflection point definingthe nosecone maximum diameter so as to reduce an average peak push forceassociated with advancing the stent mounted heart valve.

Another embodiment includes a method of delivering a stent mounted heartvalve through a sheath and into a patient vessel. An expandable sheathis inserted into a vascular structure. A capsule carrying a stentmounted heart valve is loaded into a proximal end of the expandablesheath. The method also includes reducing an average peak push forceresulting from advancement of the capsule through the sheath. Reductionis achieved by pushing the sheath away from the surface of the capsuleusing a friction-reducing feature.

DESCRIPTION OF DRAWINGS

FIG. 1 is a side elevation view of a delivery catheter assembly beinginserted into a delivery sheath of one embodiment of the presentinvention;

FIG. 2 is a side elevation view of an oversized nosecone and capsule ofanother embodiment of the present invention passing through anexpandable delivery sheath;

FIG. 3 is a side elevation view of a nosecone and capsule with afriction reducing protrusion of another embodiment of the presentinvention passing through an expandable delivery sheath;

FIG. 4A is a side elevation view of a capsule with longitudinal ridgesof another embodiment of the present invention passing through anexpandable sheath;

FIG. 4B is cross-sectional view of the capsule of FIG. 4A; and

FIGS. 5A-5D depict a self-expanding implant as it is encased bywithdrawal into a delivery capsule.

DETAILED DESCRIPTION

The following description of certain examples of the inventive conceptsshould not be used to limit the scope of the claims. Other examples,features, aspects, embodiments, and advantages will become apparent tothose skilled in the art from the following description. As will berealized, the device and/or methods are capable of other different andobvious aspects, all without departing from the spirit of the inventiveconcepts. Accordingly, the drawings and descriptions should be regardedas illustrative in nature and not restrictive.

For purposes of this description, certain aspects, advantages, and novelfeatures of the embodiments of this disclosure are described herein. Thedescribed methods, systems, and apparatus should not be construed aslimiting in any way. Instead, the present disclosure is directed towardall novel and nonobvious features and aspects of the various disclosedembodiments, alone and in various combinations and sub-combinations withone another. For example, the ridges, protrusions and/or nosecones withenlarged diameters described below could be combined in a singledelivery system. The disclosed methods, systems, and apparatus are notlimited to any specific aspect, feature, or combination thereof, nor dothe disclosed methods, systems, and apparatus require that any one ormore specific advantages be present or problems be solved.

Features, integers, characteristics, compounds, chemical moieties, orgroups described in conjunction with a particular aspect, embodiment orexample of the invention are to be understood to be applicable to anyother aspect, embodiment or example described herein unless incompatibletherewith. All of the features disclosed in this specification(including any accompanying claims, abstract, and drawings), and/or allof the steps of any method or process so disclosed, can be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive. The invention is notrestricted to the details of any foregoing embodiments. The inventionextends to any novel one, or any novel combination, of the featuresdisclosed in this specification (including any accompanying claims,abstract, and drawings), or to any novel one, or any novel combination,of the steps of any method or process so disclosed.

It should be appreciated that any patent, publication, or otherdisclosure material, in whole or in part, that is said to beincorporated by reference herein is incorporated herein only to theextent that the incorporated material does not conflict with existingdefinitions, statements, or other disclosure material set forth in thisdisclosure. As such, and to the extent necessary, the disclosure asexplicitly set forth herein supersedes any conflicting materialincorporated herein by reference. Any material, or portion thereof, thatis said to be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure material set forthherein will only be incorporated to the extent that no conflict arisesbetween that incorporated material and the existing disclosure material.

As used in the specification and the appended claims, the singular forms“a,” “an” and “the” include plural referents unless the context clearlydictates otherwise. Ranges can be expressed herein as from “about” oneparticular value, and/or to “about” another particular value. When sucha range is expressed, another aspect includes from the one particularvalue and/or to the other particular value. Similarly, when values areexpressed as approximations, by use of the antecedent “about,” it willbe understood that the particular value forms another aspect. It will befurther understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

“Optional” or “optionally” means that the subsequently described eventor circumstance may or may not occur, and that the description includesinstances where said event or circumstance occurs and instances where itdoes not.

Throughout the description and claims of this specification, the word“comprise” and variations of the word, such as “comprising” and“comprises,” means “including but not limited to,” and is not intendedto exclude, for example, other additives, components, integers or steps.“Exemplary” means “an example of” and is not intended to convey anindication of a preferred or ideal aspect. “Such as” is not used in arestrictive sense, but for explanatory purposes.

The terms “proximal” and “distal” as used herein refer to regions of theballoon, balloon catheter, or delivery catheter. “Proximal” means thatregion closest to handle of the device, while “distal” means that regionfarthest away from the handle of the device.

Disclosed herein is a delivery system for delivering a stent-mountedheart valve through an introducer sheath. The delivery system includesan elongate catheter supporting a capsule. The capsule contains thestent-mounted heart valve in the crimped condition. The delivery systemalso includes a nosecone with a tapered distal end and a proximal end.Surprisingly, the proximal end of the nosecone, despite having a largerprofile than the capsule, reduces an average peak push force foradvancing the delivery system through an introducer sheath.

Disclosed herein are tips and capsules for implant delivery cathetersthat are particularly suitable for delivery of implants in the form ofimplantable heart valves, such as self-expanding implantable heartvalves, through expandable delivery sheaths. Self-expanding implantableheart valves are well-known and will not be described in detail here. Anexample of such an implantable heart valve is described in U.S. Pat. No.8,652,202, which is incorporated herein by reference. Expandabledelivery sheaths have elastic or sectioned portions that facilitatetemporary profile expansion from the forces of the passing capsule andimplant.

The capsules disclosed herein may also be used to deliver other types ofimplantable devices, such as self-expanding (or balloon expandable)implantable heart valves, stents or filters. The terms “implant” and“implantable” as used herein are broadly defined to meananything—prosthetic or not—that is delivered to a site within a body. Adiagnostic device, for example, may be an implantable. The term“implant” as used herein also does not need to be a permanentimplant—for example devices used to deliver permanent implants are alsoimplants temporarily. An implant could be any device delivered into thebody for a procedure.

FIG. 1 illustrates a delivery catheter assembly 1 of one embodiment ofthe present invention including an elongate, expandable delivery sheath3 with a lumen to guide passage of an implant delivery cathetersupporting a prosthetic implant 5, such as a prosthetic heart valve. Ata proximal end the sheath 3 includes a hemostasis valve that preventsleakage of pressurized blood. The delivery catheter assembly 1 caninclude a steerable guide catheter 7 (also referred to as a flexcatheter). The delivery catheter assembly 1 can also include a capsule13 which can have an enlarged diameter to hold the prosthetic implant 5.The capsule 13 can, for example, restrain a self-expanding implant toprevent premature expansion prior to reaching the procedure site. Thedelivery catheter assembly 1 also includes a contoured tip or nosecone11 that can be joined with the capsule 13 to contain the prostheticimplant 5.

Generally, during use in one embodiment, the sheath 3 is passed throughthe skin of patient (usually over a guidewire) such that the distal endregion of the sheath 3 is inserted into a vessel, such as a femoralartery, and then advanced to a procedure site—such as over the aorticarch to a native aortic heart valve. The nosecone 11 and capsule 13 areinserted through the hemostasis valve at the proximal end of theexpandable sheath 3. The sheath 3 can be made at least partially of anelastic material and be expandable in the radial direction. Radialexpansion facilitates the passage of the capsule 13 and nosecone 11. Thesteerable guide catheter 7 can be used to advance the nosecone 11 andcapsule 13 through to and out of the end of the sheath 3. The nosecone11 is separated from the distal end of the capsule 13, such as byadvancement of an inner catheter 14 supporting the nosecone, asillustrated in FIG. 5A. The prosthetic implant 5 is advanced out of thecapsule 13 along with the nosecone 11 and, in the embodiment having aself-expanding stent, expands in the native heart valve or otherprocedure site as it emerges from the capsule. The process could alsoreveal a balloon-expandable stent for subsequent balloon expansion.

As shown schematically in FIG. 2, in one embodiment, a distal end of theguide catheter 7 supports the capsule 13 and the nosecone 11 is mountedon the capsule 13. The external surfaces of the nosecone 11 and capsule13 abut the adjacent, expanded wall surfaces of the delivery sheath 3.

The capsule 13, in one embodiment, has a cylindrical sleeve structurethat defines a lumen configured to hold the prosthetic implant 5 in acrimped condition. The capsule 13 shown in FIG. 2 has a proximal end 29and a distal end 31. The proximal end 29 of the capsule 13 can becoupled to the distal end of the guide catheter 7. In some embodiments,the proximal end 29 of the capsule 13 is an integral extension of atubular sheath surrounding the outside of the distal end of the guidecatheter 7. In other embodiments, the proximal end 29 of capsule 13 canbe attached to the guide catheter 7, for example, by heat shrinking.

The distal end 31 of the capsule 13 has an opening extending distallythat communicates with the lumen defined within the capsule. The lumencan be sized to hold the prosthetic implant 5 in its crimped, lowprofile state. The capsule 13 can be configured to also exertcompression stress onto the prosthetic implant 5 to hold it in a crimpedstate. For example, the tubular wall structure of the capsule 13 cansurround and have inner wall surfaces exerting restraining contactagainst outer surfaces of a self-expanding, nitinol frame stent of aprosthetic heart valve. The distal end 31 of the capsule 13 in theillustrated embodiment has a circular free edge (not shown) that can bemated with a correspondingly sized and shaped opening (not shown) in theproximal-facing surface of the nosecone. Additional details of anexemplary delivery capsule can be found in commonly assigned U.S. PatentPublication No. 2014/0343670, which is hereby incorporated herein byreference.

As shown in FIG. 2, in one embodiment, the nosecone 11 includes atapered distal end 15 and a proximal end 17. The distal end 15 of thenosecone 11 includes a distal facing surface 19 and a contoured surface21. The distal facing surface 19 can be a flat, circular surface thathas a smaller profile or diameter than the remainder of the body of thenosecone 11. The distal facing surface 19 also has about the same, orsmaller, diameter than the adjacent guide catheter 7. Generally, thedistal end facing surface 19 is sized to fit within the unexpandeddiameter of the sheath 3 and has an atraumatic (such as flat) shape forsafety reasons. Other atraumatic shapes can be rounded or hemisphericalshapes. Also, other non-circular shapes can be used for the distalfacing surface 19.

The contoured surface 21 of the nosecone 11 is, in one embodiment,axisymmetric and starts with the small diameter of the distal facingsurface 19 and expands in diameter moving proximally (towards thecardiologist holding the handle) until reaching the proximal end 17. Thecontoured surface 21 can be broken down into a progressive expansionportion 23, a rounded portion 25 and an inflection point 27. Theprogressive expansion potion 23 expands smoothly at a rate increasingwith proximal progression before splining into the rounded portion 25.The rounded portion 25 is more bulbous with a slowed expansion ofdiameter in the proximal direction until the inflection point 27, atwhich point the diameter begins to decrease moving proximally. Restated,the inflection point 27 defines the largest diameter (or noseconediameter) where the expansion in diameter of the contoured surface 21stops and then the proximal end 17 begins with a shrinking diameter.Thus, at the inflection point 27 the proximal-most boundary of thedistal end 15 (and of the contoured surface 21) and the distal-mostboundary of the proximal end 17 share the same largest diameter.

As shown in FIG. 2, the distal end 31 of the capsule 13 has a smallerdiameter than the maximum diameter of the proximal end 17 of thenosecone 11, thus the nosecone is oversized relative to the capsule.Surprisingly, the inventors have determined that this oversizingactually reduces the forces needed to advance the capsule 13 through thesheath 3 to its deployment location. Without being wed to theory, theinventors believe that the oversized diameter of the nosecone 11 pushesthe expandable sheath 3 wall away from the capsule 13 at an angle.Pushing the expandable sheath away from the capsule reduces the contactarea between the two and thus reduces the friction of the sheath 3(which includes an elastic component compressing it inwards) against theadvancing capsule 13. Also, the oversized nosecone 11 can act as adilator making the rest of the sheath 3 more compliant for the remainderof the delivery catheter assembly 1.

Notably, the term “diameter” as used herein is not limited to circularcross-sections. Instead, diameter refers to a width through a centroidof the cross-section of the shape, such as a cross-section of thenosecone 11 taken perpendicular to the long-axis of the catheterassembly 1. Although circular cross-sections are shown for the nosecone11 and/or the capsule 13, they can have other shapes, such as ovals,rounded rectangles and other shapes, including irregular shapes. Themaximum diameter of such cross-section is simply the largest diameterseen by the expandable delivery sheath 3 as the nosecone 11 and capsule13 are advanced therethrough. Generally, then the concept of enlargedprofiles for the nosecone 11 (and the capsule 13) are realized when somediameter is larger than the base capsule 13 itself needed to hold anddeliver the implant 5. Thus, the elliptical cross-section can have amajor axis that exceeds the capsule 13 and a minor axis that matches thecapsule 13 and still serves to open up the sheath 3 and reduceadvancement forces for the trailing capsule 13.

In some embodiments, the capsule 13 can be made of or coated bypolyether ether ketone (PEEK). PEEK is advantageously a lubriciouspolymer, but other lubricious materials could also be used for—or coatedon—the surfaces of the nosecone 11.

Push forces were calculated for various nosecone designs. The sheath 3used in testing was an expandable E-SHEATH from Edwards Lifesciences,Inc. (U.S. Pat. No. 8,790,387, which is hereby incorporated by referencein its entirety). The sheath 3 was extended through a model of an aortain a water bath at a temperature of 37 degrees C. A 0.035″ extra-stiffguidewire was inserted through the entire length of the aortic model.The sheath 3 with the introducer was inserted into the aortic model overthe guidewire. The water level was verified to be up to the hub of thesheath 3. The hub of the sheath 3 was secured to a force gauge plateusing a zip tie.

The proximal end of the guidewire was inserted through the catheternosecone and pushed through the catheter until being exposed from theback end of the catheter. The nosecone tip 15 was then advanced over theguidewire until positioned at the proximal side of the first seal in theintroducer housing. The force gauge was zeroed and a timer started.Then, the guidewire was pinned and the nosecone further advanced overthe guidewire and through the seal of the sheath 3. The nosecone andcapsule 11, 13 continued to be advanced through the remainder of thesheath 3 until exiting the tip of the sheath. The insertion time fromstart to finish was within 20-30 seconds. The forces, including peakpush force, and insertion time were measured. Push forces weredetermined at each 2 cm of advancement through the delivery sheath 3.

Table 1 below shows the results of the peak push force testing when thenosecone 11 was oversized by various amounts. Typically, an increase inthe diameter of the delivery capsule 13 yields higher peak push forcesdue to increased frictional forces between the capsule 13 and the sheath3. However, providing a nosecone 11 with a greater diameter than thecapsule 13 diminished the peak push forces, in some cases down to themid 20 N range. The capsule delivery cylinder outside diameter is shownin the first column and the oversizing of the nosecone 11 in thousandsof an inch is shown in the second column. The values in the oversizingcolumn represent the difference between the widest diameter of thenosecone 11 and the outer diameter of the capsule delivery cylinder. The“N” column shows the number of tests. The term UTL designates thestatistical upper tolerance limit of the data acquired from the peakpush force testing.

TABLE 1 Push Force Summary Through 14 Fr E-Sheath-PEEK Delivery Cylinder(Capsule) Delivery Nose Cone Avg Peak UTL of Peak Nosecone/ CylinderOver Sizing Push Force Push Force capsule OD (in) (in) N (N) (N)diameter ratio 0.253 0.010 2 20.5 * 1.040 0.253 0.001 2 32.5 * 1.0040.251 0.001 2 29.5 * 1.004 0.269 0.006 15 26.4 32.6 1.022 0.244 0.001 1525.3 32.6 1.004

Generally, the desired upper tolerance limit for peak force is about 45N. To meet this criteria, an average peak force of 25-30 N is targeted.Experimentation showed that the nosecone diameter being at least 1.002times the capsule diameter, for example, from 1.002 to 1.045 times thecapsule diameter, gave a peak push force upper tolerance limit of lessthan 40 N, and in particular less than 33 N. Notably the higher forceswere present in the smaller diameter oversizing.

The sheath 3 used to attain the testing values shown in Table 1 had astandard 14 French diameter. However, the size of the nosecone 11 andcapsule 13 can be adapted to other sheath sizes to attain similar valuesfor peak push forces. For example, other verification tests were runusing 16 French sheaths and CENTERA Model 9550C catheters with sizes of23 mm, 26 mm and 29 mm. The average peak push force and the uppertolerance limit of the push force were under the 40 N threshold duringthese other verification tests.

Beyond push force reduction, the oversized nosecone 11 has the advantageof being easy to manufacture (by molding). Also, the oversized nosecone11 works well with a capsule 13—especially a capsule having its distalend 31 with a thinned out wall. The thinned out wall promotes flaringfor easier withdrawal and recapture of the prosthetic implant 5 withinthe capsule 13. And, the oversized nosecone 11, because of its largerdiameter, can still mate with the flared-out distal end 31 of thecapsule 13.

FIG. 3 shows an example capsule 13 of another embodiment including oneor more bumps or other protrusions 33 positioned on the distal end 31 ofthe capsule. For example, the protrusion 33 can be an annular protrusionextending circumferentially around (in a ring) the entirety of thedistal end 31 of the capsule 13. Like the nosecone 11, the protrusion 33can have a smooth, continuous shape. The protrusion 33's configurationurges the sheath 3 away from the exterior of the capsule 13. Theprotrusions 33 thus can also reduce the average peak push forceresulting from advancement of the capsule 13 through the sheath 3.

The protrusions 33 can also include one or more rounded bumps, e.g.,hemispherical-shaped protrusions, arranged in a spaced array around thedistal end 31 of the capsule 13. The protrusions 33 could also becombined with an oversized nosecone 11.

FIGS. 4A and 4B show another example capsule 13 including a plurality ofridges 35 extending longitudinally along the outside surface of thecapsule 13. The ridges 35 are sized and spaced so as to space the insideof the sheath 3 away from the capsule 13 as it advances along the insideof the sheath 3. The ridges 35 are shown in FIG. 4A as having paralleledges extending longitudinally in the direction of the axis of thedelivery catheter assembly 1 and as having rectangular cross-sectionalshapes in FIG. 4B. The ridges 35 extend around the capsule in a spacedarrangement and are preferably 6 to 16 in number.

As illustrated in FIG. 4B, the capsule 13 can include a plurality ofridges 35 having the same height, the height of a ridge 35 measuredbetween the outer surface of the capsule and outer surface of the ridge35. It is contemplated that the capsule 13 can include a plurality ofridges 35 having different heights. As shown in FIG. 4B, an outerdiameter of the capsule 13 defined the ridges 35 can be determined bythe distance between the outer surfaces of two opposing ridges 35. Theouter diameter can also be determined by taking an average height of theridges and adding it to the diameter of the capsule 13.

Other cross-sectional shapes for ridges 35 can also be employed, such asrounded, square, irregular or semi-circular shapes. Advantageously, byadding ridges 35 along the length of the capsule 13—which defines thelargest diameter of the delivery catheter assembly 1—the frictionalforce between the capsule 13 and the inside surface of the sheath 3 maybe reduced. This is believed to be a result of changing the contact areabetween the capsule 13 and the inside diameter of the sheath 3. It isalso contemplated that the spacing between the ridges 35 could vary toreduce contact area between the capsule 13 and the sheath 3.

FIGS. 5A-D show a method of encasing a prosthetic implant 5 such as aself-expanding heart valve 5 in a capsule 13 to prepare it for delivery(or to retrieve it when needing to be repositioned within the patient).In this embodiment, the nosecone 11 includes a neck 12 positionedproximal the proximal end 17. The neck has a stepped down diameter and acylindrical shape. In the embodiment of FIG. 5A, the self-expandingheart valve 5 can be partially encased in the capsule 13 with itsproximal end coupled to the delivery system, such as the noseconecatheter. The capsule 13 is then slid distally over the remainder of theself-expanding heart valve 5 so that less of it is visible, asillustrated in FIG. 5B. As shown in FIG. 5C, the capsule 13 continuessliding distally until only the distal end of the self-expanding heartvalve 5 is visible, and it is in close proximity with proximal end 17 ofthe nosecone 11. Also, at this stage, the distal stent structure of theimplant 5 overlaps onto and can be supported by the neck 12. FIG. 5Dillustrates the capsule 13 slid completely over the self-expanding heartvalve 5 such that the distal end of the self-expanding heart valve 5 canbe sandwiched between the neck 12 of the nosecone 11 and the distal end31 of the capsule 13. Also, in this position the distal end of thecapsule 13 abuts the proximal end 17 of the nosecone 11 where itsdiameter steps up from the neck 12.

During a procedure, the process of FIGS. 5A-D can be reversed andcontinued for complete withdrawal of the capsule 13 from coverage of theimplant 5. Then the stent mounted heart valve 5 can be released (if itis self-expanding and anchored, for example) or expanded via balloon orother device. Also, if the implant is needing to be retrieved forrepositioning or removal, the procedure of FIGS. 5A-D can be repeated toretract the implant back into the capsule 13.

In view of the many possible embodiments to which the principles of thedisclosed catheter assembly can be applied, it should be recognized thatthe illustrated embodiments are only preferred examples and should notbe taken as limiting in scope. Rather, the scope of the disclosure isdefined by the following claims. We therefore claim as our invention allthat comes within the scope and spirit of these claims.

What is claimed is:
 1. A delivery system for delivering a stent mountedheart valve through a sheath, the delivery system comprising: anelongate catheter having proximal and distal ends, the stent mountedheart valve crimped at the distal end of the catheter; a capsuleextending around and enclosing the crimped stent mounted heart valve,the capsule having a distal end with a capsule diameter; and aprotrusion extending from an outer surface of the capsule for urging thesheath away from the capsule, thereby reducing an average peak pushforce resulting from advancement of the capsule through the sheath. 2.The delivery system of claim 1, further comprising: a nosecone coupledat its proximal end to a distal end of the capsule, the noseconeincluding a tapered surface having a gradually increasing diameter froma distal end of the nosecone towards the proximal end of the nosecone;an inner catheter extending through the elongate catheter, capsule andstent mounted heart valve, the inner catheter supporting the nosecone onits distal end, wherein distal advancement of the inner catheterrelative to the elongate catheter advances the stent mounted heart valveout of the capsule.
 3. The delivery system of claim 1, wherein a maximumdiameter of the protrusion is greater than a maximum diameter of thedelivery system.
 4. The delivery system of claim 1, wherein a maximumdiameter of the protrusion is at least 1.002 times the capsule diameter.5. The delivery system of claim 4, wherein the maximum diameter of theprotrusion is 1.002 times to 1.045 times the capsule diameter.
 6. Thedelivery system of claim 5, wherein an upper tolerance limit of the peakpush force is less than 40 Newtons.
 7. The delivery system of claim 5,wherein an upper tolerance limit of the peak push force is less than 33Newtons.
 8. The delivery system of claim 1, further comprising theexpandable delivery sheath, the sheath having a central lumen sized andconfigured to receive the elongate catheter and the capsule, wherein thecentral lumen defines a starting inner diameter less than the capsulediameter.
 9. The delivery system of claim 1, wherein the protrusion hasa smooth and continuous surface.
 10. The delivery system of claim 1,wherein the protrusion is positioned on a distal region of the capsuleand extends circumferentially around at least a portion of the diameterof the capsule.
 11. The delivery system of claim 10, wherein theprotrusion defines a ring shape and extends around an entirety of thediameter of the capsule.
 12. The system of claim 1, wherein theprotrusion includes a plurality of longitudinally extending ridgesprotruding from the outer surface of the capsule.
 13. The deliverysystem of claim 12, wherein the plurality of longitudinally extendingridges includes at least 6 ridges.
 14. The delivery system of claim 12,wherein the capsule has an extruded cross-section and wherein thelongitudinally extending ridges have an angular cross-sectional shape.15. The delivery system of claim 14, wherein the longitudinallyextending ridges have a rectangular cross-sectional shape.
 16. Thedelivery system of claim 12, wherein the longitudinally extending ridgesextend around a circumference of the capsule, are spaced from each otherin a circumferential direction and define troughs between each pair oflongitudinally extending ridges.
 17. A delivery system for delivering astent mounted heart valve through an expandable sheath, the deliverysystem comprising: an elongate catheter having proximal and distal ends,the stent mounted heart valve crimped at the distal end of the catheter;a capsule sized and configured to extend around and enclose the crimpedstent mounted heart valve, the capsule having a distal end with acapsule diameter, the capsule including a protrusion extending from anouter surface of the capsule and having a protrusion diameter greaterthan the capsule diameter, the protrusion urging the sheath away fromthe capsule, thereby reducing an average peak push force resulting fromadvancement of the capsule through the sheath; and a nosecone coupled atits proximal end to a distal end of the capsule, the nosecone includinga tapered surface having a gradually increasing diameter from a distalend of the nosecone towards the proximal end of the nosecone.
 18. Thedelivery system of claim 17, wherein the proximal end of the noseconedefines a nosecone maximum diameter, where the nosecone maximum diameteris greater than the capsule diameter.
 19. The delivery system of claim18, wherein the nosecone maximum diameter is less than the protrusiondiameter.
 20. The delivery system of claim 17, further comprising theexpandable delivery sheath, the sheath having a central lumen sized andconfigured to receive the elongate catheter, capsule and nosecone,wherein the central lumen defines a starting inner diameter less thanthe capsule diameter.